Re: [RFC PATCH 11/56] x86/bugs: Reset MMIO mitigations

Borislav Petkov
2026-01-26T13:06:20Z

On Mon, Oct 13, 2025 at 09:33:59AM -0500, David Kaplan wrote:
> Add function to reset MMIO mitigations back to their boot-time defaults.
>
> Signed-off-by: David Kaplan <david.kaplan@amd.com>
> ---
> arch/x86/kernel/cpu/bugs.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 5668a8b8821b..9139c8187913 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -787,6 +787,16 @@ static void __init mmio_apply_mitigation(void)
> cpu_smt_disable(false);
> }
>
> +#ifdef CONFIG_DYNAMIC_MITIGATIONS
> +static void mmio_reset_mitigation(void)
> +{
> + static_branch_disable(&cpu_buf_vm_clear);

This needs to be

setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM_MMIO);

I believe, after:

f6106d41ec84 ("x86/bugs: Use an x86 feature to track the MMIO Stale Data mitigation")

--
Regards/Gruss,
Boris.